The present invention, generally, relates to improvements to spray guns and nozzle attachments and, in particular, to foam spray guns adapted to have controlled metering of at least two components, and to disposable attachable nozzles adapted to prevent crossover of chemically reactive fluids.
Polyurethane foams are utilized for packaging, insulation, and in shaping and coating of articles. Two or more chemically reactive fluid resins under pressure pass through separate channels of a spray gun, eventually, are allowed to mix in a mixing chamber of a nozzle from which the resultant foam product. polyurethane, is dispensed. The two resins, xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d, each have a different viscosity. Resin xe2x80x9cAxe2x80x9d, polymeric isocyanate, is about twice as viscous as resin xe2x80x9cBxe2x80x9d, polyol amine, and, thus, resin xe2x80x9cAxe2x80x9d exhibits a higher resistance to flow under the same flow conditions compared to resin xe2x80x9cB.xe2x80x9d
Under pressure, each of the two liquid resins passes separately into the different channels within the spray gun. Each channel has a plunger/needle which when urged forward by a coiled spring prevents the passage of either resin out of the inlet ports and out of discharge openings of tie spray gun. When a trigger is pulled, coiled springs are compressed, plungers move rearward thereby allowing each liquid resin to pass out each inlet port into its respective channel around its respective plunger and out its respective discharge opening into a nozzle. There is no dispensing of the more viscous resin at low metering rates when the trigger of the gun is only slightly depressed. On the other hand, there is good dispensing at high dispensing rates of both resins when the trigger of the gun is depressed completely. This, the difference in viscosity between the two resins influence the relative flow rates at low dispensing rates. This difference at low dispenses rates, concomitantly, results in poor expanding and curing of the polymer, an off-ratio resin flow into the nozzle. A standard needle valve spray gun is disclosed in U.S. Pat. Ser. No. 5,462,204 to Clifford J. Finn.
When liquid resin xe2x80x9cAxe2x80x9d and liquid resin xe2x80x9cBxe2x80x9d are mixed together in the proper amounts in a thorough manner, a polymerization reaction occurs. The resultant settable polymer product can harden, clog and block channels of the gun, thus, the two resins are kept separate and apart within different channels of the gun and are only allowed to mix after passing into the nozzle before being dispensed.
The two components are suppose to be under the same pressure, however, practically, it is not possible to maintain the same pressure in the reservoir tanks of resin xe2x80x9cAxe2x80x9d and xe2x80x9cB.xe2x80x9d Under certain conditions, the component with the higher pressure can crossover and contaminate the component with the lower pressure leading to formation of clogs.
In addition, once dispensing of the polymer ceases, any polymer remaining in the nozzle will harden, clog if exposed to air and moisture, block and prevent the reuse of the nozzle.
While each of the resins is tinder pressure within its channel there can be leakage problems within the spray gun and there can be leakage problems at the connection between the nozzle and tile spray gun.
Accordingly, to overcome the disadvantages of the prior art spray guns and nozzle attachments, it is an object of the present invention to provide a controlled metering system for a range of metering rates from low to high rates and to prevent crossover of either resin.
It is another object of the present invention to provide a seal means to aid in the metering of each resin.
It is still another object of the present invention to provide a seal means to prevent leakage of the
It is still another object of the present invention to provide a seal means to prevent leakage of the resins while the resins are under pressure.
It is a further object of the present invention to provide a means for preventing the leakage of either resin rearward within the spray gun.
It is still another object of the present invention to provide a configuration to both the tip of the plunger and of the discharge opening of the spray gun to prevent air or moisture from reacting with either resin and clogging its respective channel.
It is a further object of the present invention to provide a means of preventing resin crossover within the nozzle.
It is another object of the present invention to provide a means to seal the nozzle to the discharge opening of the spray gun to prevent leakage of the resins at the connection.
It is still another object of the present invention to provide an attachment means for securing the nozzle to the spray gun to prevent any leakage.
It is yet still another object of the present invention to provide a quick and easy means of attaching/detaching the nozzle to the spray gun.
The invention provides both for a dispensing gun having a ramp-shaped slot on each resin passageway""s inner bore for controlled metering of each resin and for a nozzle attachment having two identical one-way valves within its inlet opening to prevent resin crossover.
In its broader aspects, the spray gun of the present invention is a body consisting of a trigger, a first and a second longitudinal barrel, and a first and a second longitudinal metering chamber forward of each of the barrels and secured thereto. Within each of the first and second barrels and each of the first and second metering chambers are continuous first and second longitudinal passageways. The first and second passageways are defined by continuous first and second inner bores within the barrels and the metering chambers. Within the passageways are a first and a second inlet port connected to sources of a first and a second resin, and within tile first and second passageways are a first and a second plunger to individually meter the first and second resin. A spring is around each of the first and second plungers to urge the first and second plunger to a closed position. A ramp-shaped slot is disposed into the first and second inner bores for controlled metering of the resins.
In its broadest aspects, there is a nozzle attachment to a foam-dispensing gun. The nozzle has two one-way valves to prevent any crossover of resins. The nozzle has a mixing chamber for mixing the resins. The nozzle has an inlet opening for receiving each of the resins and an outlet opening for dispensing the reaction product of mixing the resins in the mixing chamber.
In its broadest aspects, the combination of the gun and the nozzle attachment include a body consisting of a trigger, a first and a second longitudinal barrel, and a first and a second longitudinal metering chamber forward of each of the barrels and secured thereto. Within each of the first and second barrels and each of the first and second metering chambers are continuous first and second longitudinal passageways. The first and said second passageways are defined by continuous first and second inner bores of the barrels and the metering chambers. Within the passageways are a first and a second inlet port connected to sources of a first and a second resin. Within the first and second passageways are a first and a second plunger to individually meter the first and second resin. A spring is around each of the first and second plungers to urge the first and second plunger to a closed position. A ramp-shaped slot is disposed into the first and second inner bores for controlled metering of the resins. A nozzle has an inlet opening for receiving each of the resins from the gun, an outlet opening for dispensing a polyurethane foam from the nozzle, a mixing chamber and two one-way valves to prevent crossover of the resins within the gun.
The various features and advantages of the invention will become more apparent from the detailed description of a preferred embodiment of the invention when considered along with the accompanying drawings.